1. Field of the Invention
This invention relates broadly to laboratory equipment. More particularly, this invention relates to test tubes and test tube racks.
2. State of the Art
Standard test tubes are tubular in shape and have a rounded sealed bottom end and an open top end. The standard test tube design possesses a high degree of utility in laboratory experimentation and research. In fact, it is anticipated that the standard shape test tube will continue to dominate the test tube market due to its simplicity and design familiarity. Yet, this dominance is in spite of drawbacks associated with the standard design.
Standard test tubes require the use of a rack for support, as the test tubes cannot stand on their own. Unless the open end of a standard test tube is closed with a stopper, when the test tube is placed on a flat surface without the use of a rack, the contents of the test tube will spill out. Therefore, standard test tubes, regardless of size, generally require the use of a test tube rack to hold the test tubes while the test tubes are being utilized. As a result, when placing a standard test tube into a heated water bath, the test tube must first be placed into a test tube rack and then the entire rack must be inserted into the water, such that the test tubes are substantially submerged. This results in more time and energy needed to bring the contents of the standard test tubes to the desired temperature. Furthermore, as a substantial portion of the standard test tube is submerged in the water bath, it is difficult to monitor reactions occurring within the test tube. Moreover, when applying heat to a standard test tube, it is common to place the test tube in a clamp and to apply a flame under the test tube. This often provides uneven heating of the contents, as heat is applied primarily only under the bottom of the test tube and may cause the contents at the bottom of the tube to scorch. In addition, standard test tubes cool slowly as cool air will only come into contact with a small surface area of the contents of the tube. Another disadvantage is that when adding or heating reagents in a standard test tube there is a strong potential for harmful spatter from "bumping" (the rapid evolution of gas bubbles) to occur which can result in sample loss. Furthermore, when adding a substance to a test tube in situations where the substance weight is critical, the substance must first be weighed on weighing paper and then transferred into the test tube. As some of the substance will remain on the weighing paper after the bulk of the substance has been transferred to a test tube, experimental error is introduced into the system.
As discussed above, standard test tubes require a test tube rack. Standard test tube racks usually have upper and lower horizontal holding members and vertical supports. The upper holding member has a plurality of holes arranged in a two dimensional array, each of the holes being slightly larger than the diameter of the standard test tubes which the rack is designed to hold. The lower holding member has a plurality of depressions aligned below the holes of the upper holding member. A standard test tube extends through one of the holes in the upper holding member and seats in the depression aligned beneath the hole through which the test tube extends.
Standard test tube racks, like standard test tubes, also carry substantial disadvantages. First, it is difficult to monitor and observe reactions occurring in a test tube held in a standard rack if the test tube is not located along the edge of the two-dimensional array. This problem is compounded when a large number of tubes fill the rack, making observation of the contents below the mouths of the tubes even more difficult. Second, standard racks require a substantial amount of space, as their design is not generally conducive to stacking. In those racks which are stackable, once the racks are stacked, observation of a test tube within a lower rack is not possible and removal of a test tube from a lower rack requires removing the racks stacked above the lower rack.